Human powered vehicles provide fundamental and often the sole means of transportation for millions of people throughout the world. For people with particular types of disabilities, such vehicles provide a means to a less encumbered lifestyle. A primary component of human powered vehicles is the drive system. Biomechanical forces transferred to an input device, such as a ring, handle or pedal, must be transferred to a driving device such as a wheel or track. Traditional drive systems on bicycles are comprised of pedals, a crankshaft, chain ring, chain and sprocket on the driving wheel. To achieve variability in torque and speed relationships between the input (pedals) and output (drive wheel), multiple size chain rings and sprockets are typically used. Hand- powered cycles use a similar drive system. The design of human powered cycle drive systems has remained relatively unchanged for decades. Fundamental shortcomings inherent in the original design remain in present day applications. Chain jamming, misfeeds resulting in a chain-off chain ring or sprocket condition, and chain filth remain at the forefront of design deficiencies. The inability to shift gears under power and the misalignment of the chain in all but a few gear combinations results in significant inefficiencies for the operator. A newly developed cycle drive system is finally able to address these problems. The Powershift Variable Speed Transmission (PVST) system is a multi-gear solution that can be used with a belt or chain. Shifting occurs by changing the diameter of the "gears" instead of moving the chain/belt to a different gear. Various virtual PVST design development efforts have already been completed. The objectives of the proposed project include;the development of physical prototypes for hand-powered cycles;completion of functional laboratory tests of the system;installation of the system on a hand powered cycle;and obtaining feedback on the design and application through the use of end-user focus groups. The hand powered cycle application has been chosen for the following reasons: (i) the potential benefits to individuals (both military and civilian) worldwide injured in military conflicts, ii) the potential benefits to individuals with limited lower extremity function due to other causes, (iii) the availability of experienced, local, expert resources such as the Human Engineering Research Labs (HERL), affiliated with the Shuman Veterans Facility and the University of Pittsburgh to assist in the testing and evaluation of the system, (iv) lessons learned and the experience gained through this application can be transferred directly to broader applications such as traditional bicycles. The intended short term and long term goals of this project are aligned with the mission of the NIH, namely;the extension of healthy life, in this case through the promotion and improvement in the efficiency and function of human powered vehicles;and the reduction of the burdens of illness and disability, to be achieved by applying a potentially lower cost, technologically advanced, cleaner, more efficient and safer drive system design to mobility systems specifically developed for the disabled. PUBLIC HEALTH RELEVANCE: Health and quality of life are intertwined and generally associated with an individual's independence and self-sufficiency. For the physically impaired, independence and self-sufficiency requires mobility. The proposed project offers major improvements in the efficiency, performance and safety of hand cycles used by the disabled through the application of advanced technology materials and innovative drive system designs.